1610s, perhaps from Dutch kooi "cage," used of a pond surrounded by nets, into which wildfowl were lured for capture, from West Germanic *kaiwa, from Latin cavea "cage." The first element is possibly the Dutch definite article de, mistaken in English as part of the word. But decoy, of unknown origin, was the name of a card game popular c. 1550-1650, and this may have influenced the form of the word.

1963, "to reform a criminal," back-formation from decriminalization. Meaning "to make legal something that formerly had been illegal" was in use by 1970 (there are isolated instances back to 1867). Related: Decriminalized; decriminalizing.

1610s, from French decrier (14c.; Old French descrier "cry out, announce"), from de- "down, out" (see de-) + crier "to cry," from Latin quiritare (see cry (v.)). In English, the sense has been colored by the presumption that de- in this word means "down."

1650s, from Latin decussatus, past participle of decussare "to divide crosswise, to cross in the form of an 'X,'" from decussis "the figure 'ten'" (in Roman numerals, represented by X) from decem "ten" (from PIE root *dekm- "ten"). As an adjective, from 1825.

late 14c., "action of dedicating," from Old French dedicacion (14c., Modern French dédication) "consecration of a church or chapel," or directly from Latin dedicationem, noun of action from dedicare (see dedicate). Meaning "the giving of oneself to some purpose" is c. 1600; as an inscription in a book, etc., from 1590s.

early 15c., "action of deducting," from Middle French déduction or directly from Latin deductionem (nominative deductio), noun of action from past participle stem of deducere (see deduce). Meaning "that which is deducted" is from 1540s. As a term in logic, from Late Latin use of deductio as a loan-translation of Greek apagoge.

Old English deman "to judge, condemn, think, compute," from Proto-Germanic *domjan, denominative of *domaz, from PIE root *dhe- "to set, put" (compare doom). Originally "to pronounce judgment" as well as "to form an opinion." The two judges of the Isle of Man were called deemsters in 17c., a title formerly common throughout England and Scotland and preserved in the surname Dempster.

Figurative senses were in Old English; extended 16c. to color, sound. Deep pocket "wealth" is from 1951. To go off the deep end "lose control of oneself" is slang first recorded 1921, probably in reference to the deep end of a swimming pool, where a person on the surface can no longer touch bottom. When 3-D films seemed destined to be the next wave and the biggest thing to hit cinema since talkies, they were known as deepies (1953).

"place where something is discarded," by 1921 (in phrase give (something) the deep six), originally in motorboating slang, perhaps from earlier underworld noun sense of "the grave" (1929), which is perhaps a reference to the usual grave depth of six feet. But the phrase (in common with mark twain) also figured in the sailing jargon of sounding, for a measure of six fathoms:

As the water deepened under her keel the boyish voice rang out from the chains: "By the mark five--and a quarter less six--by the deep six--and a half seven--by the deep eight--and a quarter eight." ["Learning the Road to Sea," in "Outing" magazine, Feb. 1918]

Old English deor "animal, beast," from Proto-Germanic *deuzam, the general Germanic word for "animal" (as opposed to man), but often restricted to "wild animal" (source also of Old Frisian diar, Dutch dier, Old Norse dyr, Old High German tior, German Tier "animal," Gothic dius "wild animal," also see reindeer), from PIE *dheusom "creature that breathes," from root *dheu- (1) "cloud, breath" (source also of Lithuanian dusti "gasp," dvesti "gasp, perish;" Old Church Slavonic dychati "breathe").

For prehistoric sense development, compare Latin animal from anima "breath"). Sense specialization to a specific animal began in Old English (usual Old English for what we now call a deer was heorot; see hart), common by 15c., now complete. Probably via hunting, deer being the favorite animal of the chase (compare Sanskrit mrga- "wild animal," used especially for "deer"). Deer-lick is first attested 1778, in an American context.